The application generally relates to a device and method for cryptography. The application relates more specifically to a device and method of a computational optical physically unclonable function (COPUF).
Physical unclonable functions (PUFs) are tools used in cryptography to create easily observed but difficult to predict outputs tied to the physical properties inherently unique to a particular device. Most PUF technology has focused on electrical systems, but electrical systems require the presence of embedded electronics. Alternative PUFs that rely on macro-scale interactions from optical effects, which are simpler to measure, have been explored. However, these optical PUFs are expensive and bulky, and have traditionally required coherent illumination (i.e., lasers). A PUF is needed that can be utilized where electronic PUFs cannot, or in applications where custom embedded electronics are not available, all while using cost-effective components.
A physical unclonable function (PUF) is a system that embeds a unique fingerprint into a device, either using existing hardware structures (intrinsic PUFs), or by purposely introducing a random element into a system (extrinsic PUFs). These devices have numerous cryptographic applications across many domains of security. Integrated circuit (IC) PUFs have been studied and implemented. IC PUFs have many advantages, but require the presence of integrated circuits (ICs). Photonic based PUFs fall into two categories: coating-based PUFs and optical PUFs. Coating-based PUFs include a coating that may be applied to an RFID device, or tag, and attached to an item. Optical PUFs rely on speckle statistics which requires coherent illumination. However, current optical PUFs suffer from a number of practical deficiencies, including sensitivity to the alignment of the laser or coherent light source and the use of bulky and expensive components.